The first preliminary set of measurements of the drug binding enthalpies for daunomycin to DNA in the 10-20 micromolar range (where the monomeric form predominates) have been made. These results were presented in a poster session at the 1988 meeting of the Biophysical Society. The enthalpies at these concentrations were in the 30-50 microjoule range. With a tantalum stopped flow calorimeter, we were able to measure 120 of these reactions per day with an uncertainty of only 3 microjoules. We anticipate two more sets of experiments to explore the salt and temperature dependence of the enthalpies. The experiments are being performed in collaboration with the Bureau of Biologics of the FDA.